F4 B6 CELL DIVISION

Question 1

State the 2 stages of cell division

Answer 1

• karyokinesis (division of nucleus)

- cytokinesis (division of cytoplasm )

Question 2

What is cell cycle?

Answer 2

the sequence of events that involves DNA multiplication and cell division to produce 2 daughter cell.

Question 3

What is mitosis?

Answer 3

the division of the nucleus of parent cell into 2 nuclei

Question 4

Explain prophase in mitosis

Answer 4

• chromatin shorten and thicken
• both sister chromatids joined at the centromere
• nucleus membrane disintegrate
• nucleolus disappears
• centriole move to opposite poles
• spindle fibers form

Question 5

Explain metaphase in mitosis

Answer 5

• centrioles at opposite poles of cell
• spindle fibers maintain chromosomes at equatorial plane
• chromosomes aligned in single row
• centromere begins to divide.

Question 6

Explain anaphase in mitosis

Answer 6

• centromere divides into 2
• sister chromatids separate
• spindle fibers shorten, contract
• sister chromatids attracted to opposite pole
• chromatids arrives at pole of cell

Question 7

Explain telophase in mitosis

Answer 7

• chromatids now called daughter chromosomes
• each pole contains 1 set of complete and identical chromosomes
• chromosomes shaped to fins chromatin threads
• nucleoli formed
• spindle fibers disappear
• new nucleus membrane formed

Question 8

What is meiosis?

Answer 8

process of cell division that occurs in reproductive organs to produce gametes

Question 9

Explain prophase I in meiosis

Answer 9

• chromatin shortens, thickens and forms chromosomes
• nucleus membrane & nucleoli disappear
• both centrioles move to opposite poles
• spindle fibers form

Question 10

Explain metaphase I in meiosis

Answer 10

• homologous chromosome arranged at equatorial plane
• sister chromatids still tied together
• centromere not separated

Question 11

Explain anaphase I in meiosis

Answer 11

• spindle fibers contract
• each homologous chromosomes separate from its homologous pair
• pulled to opposite poles
• sister chromatids still tied together
• centromere not separated

Question 12

Explain telophase I in meiosis

Answer 12

• chromatids arrive at opposite poles
• spindle fibers disappear
• nucleoli reappear
• nuclear membrane formed
• cytokineses to produce 2 daughter cell. ( haploid )

Question 13

Whats the point where the chromatids cross over?

Answer 13

chiasma

Question 14

Explain prophase II in meiosis

Answer 14

• nucleoli and nuclear membrane disappear
• chromosome made up of sister chromatids
• spindle fibers from

Question 15

Explain metaphase II in meiosis

Answer 15

• chromosomes arranged on equatorial plane
• each chromatid tied to spindle fibers at centromere
• centromere separates

Question 16

Explain anaphase II in meiosis

Answer 16

• sister chromatids centromere separate
• sister chromatids separates & move towards opposite poles
• chromatids = chromosome

Question 17

Explain telophase II in meiosos

Answer 17

• chromosomes at pole of cell
• spindle fibers dissapeared
• nucleoli formed
• nuclear membrane formes
• cytokinesis occur to produce 4 daughter cells. ( haploid )

Question 18

What are the types of tumour?

Answer 18

1. benign tumour ( not dangerous; surgically removed)
2. malignant tumour ( cancer; radiation, chemical substance, carcinogens)
   - cells divide continuously and develop a tumour.
   - cancer cells spread & destroy normal cells

Question 19

What will happen if any abnormality occurs during meiosis?

Answer 19

• down syndrome (47 chromosomes)
• spindle fibers failed to function in anaphase I/II
• chromosomes failed to function
• abnormal number of chromosomes ( 22,24 )
• extra at 21st set (trisomy 21)
• mental retardation, slanted eyes, protruding tongue.